It is customary to retain, i.e. clamp, gears or like workpieces in a chuck by the intervention of a roller cage. This roller cage is comprised of a metal ring with a row of rollers arranged on resilient wires. The individual roller rows are adapted to the gaps between the teeth of the gear wheels or gears. Such a roller cage is initially introduced into the gaps of the gear wheel and the cage is then introduced with the gear as an assembly into the chuck. The chuck jaws then engage the rollers and damage of the gears by the chuck is prevented.
During each workpiece replacement, in a special operational step, the roller cage must be slipped over the new workpiece. Following machining the workpiece, the roller cage must be taken off, and then cleaned, in order to be ready again for the next workpiece. Accordingly, the time required for workpiece exchange is relatively lengthy and furthermore automation of the workpiece exchange is nearly impossible.